Abstract : This report concerns itself with the neutron energy distribution of the east port of the water boiler with a U(235) source inserted. The work was done with nuclear plates and provides reliable data in the energy region from 0.5 to 6 Mev. The report is essentially a supplement to LA-718 which deals with the identical neutron spectrum in the energy region from 3.3 to 17 Mev. In addition to extending the knowledge of the neutron spectrum of the water boiler fast beam, the experiment also gives information on the influence of a collimating tube on a neutron spectrum.